The little boy was immediately drawn to a replica sheriff’s badge.
“He put it on,” recalled his mother, Esther. “He loved his badge, [even] as he got older. He said ‘One day, I’m going to protect the president of the United States.’”
Eventually, Herrera got to wear a real badge.
He didn't protect the president, but he did make his mark as a detention officer and then a deputy in the El Paso County Sheriff’s Office.
Herrera, 35, took his role as guardian of law and order especially seriously. Friends say he was focused -- and often hard on himself.
“He was straightforward, I was a joker,” said Deputy Adrian Gonzales, who became close buddies with Herrera. “He was very serious. He didn’t like social media. Sometimes people pick on their trainees [as a sort of rite-of-passage], but not him, he was very professional all the time.”
When off-duty, Gonzales said, “Pete was the type, if he didn’t like you, he let you know. If he did, he took care of you.”
They became friends by happenstance.
Gonzales, 39, was working with weights at the gym when Herrera, whom he had seen at work but never chatted with, came up to him.
“He said ‘Hey, you work in the annex, right?’” Gonzales said. They spoke a bit more and Herrera said “'If you ever need a spotter, let me know.' I said ‘I need a spotter right now,’ and he said ‘O.K., I got you.’ And from that day, we started working out together.”
After a vigorous workout, Gonzales said, laughing, “We’d go to Applebee’s, have chocolate cake.”
Herrera was close with his siblings, and was particularly close to his mother, being the only child of hers who still lived in Texas.
She enjoyed cooking for him, and his favorite was homemade spaghetti.
“Ever since he became a law enforcement officer he worked different shifts,” she said, “I didn’t care what time he would come home, if he was hungry, if he wanted to have a steak, I’d make him a steak.”
Herrera was her miracle baby. He was born prematurely, weighing only 3 pounds.
“We could have lost him when he was born,” she said. “He had to stay in the hospital for a month and a half.”
Esther Herrera had many philosophical conversations with her son and her other kids.
“I always said ‘Be humble and smile, sometimes that person you come face to face with needs a smile,’” she said.
Another piece of advice she dispensed: “If you’re going to do something, do it right or don’t do it at all. Give it your best.”
Since her son was in a job that at times put him in mortal danger, she tried to raise the issue of being targeted for violence.
“Several times I said ‘We need to talk about reality,’” she said. “I said ‘I respect what you do, but we need to talk about what if.’”
Herrera simply replied: “Mom, I’m going to give it my all."
But with Gonzales, Herrera did discuss the dangers.
“We talked about that a lot,” Gonzales said. “He said ‘Don’t leave me on life support.’ He was very serious about it, he’d always talk about that. He said ‘We all should take it seriously.’”
On the night he was shot, he called Gonzales – with whom he often did off-duty security work -- hours earlier to plan what bars they would work together after he completed his shift.
And even though he had married four months earlier, Herrera often still stopped by his mother’s house, and did so on his last afternoon.
“I fed him before he went to work, and I always washed and pressed his uniform,” his mother said. “I was blessed to see him that day.”
During his shift on March 22, Herrera pulled over a car for a registration violation and instructed the driver to step out. When the driver did, officials say he fired 15 rounds at Herrera. Herrera was taken to a hospital and, after initially appearing to respond well to surgery, he took a turn for the worse and died two days later.
Esther Herrera said she tries to be philosophical as she mourns her son, and so she thinks of that little fragile newborn fighting to live.
"I used to say 'If for any reason the Lord calls you, I will say Thank you,'" she said. "I thank the Lord for the 35 glorious years he gave him to me. I have wonderful memories."
The murder trial will be painful, she knows that. To lose a child -- in any way -- is tortuous enough. But to know that he was shot over and over and over, and was alive with his injuries for two days, brings unfathomable despair.
"I stopped watching the news after this happened," she said. "I have to be strong when the trial comes, I ask God to give me the strength to sit there through the trial."
In the meantime, she fills her mind and heart with what matters in the long run: "You can close your eyes, and picture that person who has left this earth, and that’s what keeps you going."